This is our baby, sleeping with her little bottom in the air. Lately, it's been pretty hot so she's sleeping with no pj's! At night, when we put her down, we give her water before she goes to bed, then a few hours later before we lay down to sleep, we give her a little more. When we first started doing this a few weeks ago, she would stir and wake up when we'd give her water. Now, the little girl just sleeps right through it. We can roll her over, put the little sippy cup to her mouth, she drinks it and rolls back over without batting an eye. This is now known as sleeping through hydration.